Sliding vane rotary pumps have a multitude of mechanical and industrial applications and as such are subject to a wide range of environmental conditions. More specifically, sliding vane rotary pumps are used in aircraft which subjects the pumps to severe atmospheric conditions having widely varying partial pressures of natural film-forming atmospheric constituents such as water vapor and oxygen. This causes the pumps to experience undue wear and thus greatly shortens their operating life.
Previously, mechanical carbon parts such as disclosed in U.S. Pat. No. 3,191,852 to Kaatz et al. issued June 29, 1965, which are normally formed of powdered graphite and carbon with a suitable binder, have been employed in aircraft.
These carbon parts have proved to be less than satisfactory as wear continues to occur due to the frictional contact between the relatively moveable parts when operated under the above-described atmospheric conditions. This places some limits on the operating life of such pumps.
In addition, the fragile nature of such carbon parts occasionally results in their chipping or fracture when in use, thereby requiring the pump to be repaired at frequent intervals.
The present invention comprises a rotary pump with sliding vanes which overcomes the foregoing disadvantages of the prior art. More specifically, the disclosed sliding vane rotary pump has a self-lubricating solid coating covering the exterior end facing surfaces of the rotor and end facing surfaces of the air transfer end plates. In addition, there is an internal pair of bushings centrally located in the rotor, whose bearing facing surfaces are covered with a self-lubricating solid coating.
Moreover, the self-lubricating solid coating is of a type of composition which alleviates the need of using the heretofore carbon parts.
As such, a pump constructed to include the present invention is capable of long-term use while inhibiting wear between the rotor and vanes even under the divergent atmospheric conditions of varying partial pressures such as encountered in aircraft operations.